Patients suffering from macula degeneration usually have impaired central visual fields and often rely heavily on peripheral vision, i.e. vision provided by the peripheral retina around the center of the macula, for daily tasks. Peripheral retina has low receptors (cons and rods) densities, which gives rise to a relatively poor resolution ability.
Such patients suffering from (age-related) macular degeneration are usually generally referred to as AMD patients. They often have compromised fovea at the center of the macula. However, there are still functional retina receptors surrounding the compromised receptors. These functional retina receptors are often peripherally located and have a larger spacing between each other. The increased spacing leads to decreased image resolution ability of the retina. For example, at 3 degrees nasal retina, the visual acuity is reduced to 0.4 compared to an 1.0 visual acuity at 0 degrees; at 5 degrees nasal retina, the visual acuity is reduced to 0.34 compared to the 1.0 visual acuity at 0 degrees.
There are three basic types of vision aids available conventionally for patients suffering from (age-related) macula degeneration, which can be applied either individually or in combination. A first type is a single telescope as the visual aid. Such telescopes are often mounted on spectacles, which are heavy and are not appealing cosmetically. Telescopes can also be implanted, which generally requires very large incisions during surgery to implant. The main disadvantage of using a telescope system alone is the resultant narrow visual field of view and overall poor image quality, which could cause a safety concern during normal daily activities.
A second type of vision aid is a prism. The prism is to realign the line of sight to the peripheral retina. This application needs to overcome a binocular fusion problem in order to avoid double imagery. The prism does not magnify the retinal images and therefore, the problem of low visual resolution due to the larger peripheral retina receptor spacing is not resolved.
A third type of vision aid is a magnifying glass, sometimes combined with a prism. This visual aid is often used as a desk-mounted device, which limits the application range for patients. A handheld version of this visual aid has vision instability and focus problems for patients with hand tremors.
Several alternatives have been developed and are based on “implantable optics”. U.S. Pat. No. 4,759,761 discloses an intraocular lens which has interior mirrored surfaces forming a folded telescope of either the Gregorian type or the Cassegrain type.
US 2007/0276483 also discloses an intraocular telescopic lens formed by implantation of a negative lens and a positive lens with a spacer in between them.
US 2007/0182917 A1 discloses a diffractive multifocal lens, which in fact is an intraocular lens providing at least two powers of magnification. The optic has zone structures providing an added optical power over 6 dioptres in addition to a base optical power and is intended for use by AMD patients. Diffractive optics structures are inherently causing chromatic aberration and considerable halo's, glare and at loss of light energy of at least 20%, which reduces contrast sensitivity.
US 2009/0048671 discloses an intraocular implant with optical elements adapted to form images on the retina. It has at least one mirror operationally connected to the action of the ciliary muscle.
There are many types of intra ocular lenses that have been especially designed as an aid for patients which suffer from macular degeneration or which have another macula-related problem. All known designs have disadvantages, for instance, providing halo's, loss of light, or loss of visual resolution.
GB 2 468 367 A discloses adding a (second) intra-ocular lens in addition to the natural eye lens (or in addition to an intra-ocular lens replacing the natural eye lens). The (second) intra-ocular lens has its optical parallel but shifted with respect to the (intra-ocular lens replacing the) natural eye lens, and is arranged behind the (intra-ocular lens replacing the) natural eye lens along the optical axis of the (intra-ocular lens replacing the) natural eye lens. Both lenses therefore provide an imaging system that jointly project an image onto the macula of the eye such that the focal point is shifted away from the fovea. The imaging system of both lenses effectively only has one optical axis.
WO 2010/131955 A1 discloses an intra-ocular lens for replacing the natural eye lens. The intra-ocular lens comprises two optical elements which overlap along the optical axis to jointly project an image onto the macula of the eye. One of the optical elements can be shifted in a direction perpendicular to the optical axis, and optionally tilted, to tilt the optical axis and shift the image to a healthy sector of the macula.
U.S. Pat. No. 5,354,334 also discloses an intra-ocular lens for replacing the natural eye lens and comprising two optical elements which overlap along the optical axis to jointly project an image onto the macula of the eye. One of the optical elements can again be shifted in a direction perpendicular to the optical axis. The intra-ocular lens of the two optical elements disclosed in U.S. Pat. No. 5,354,334 and WO 2010/131955 A1 effectively only has one optical axis.